• Korean Journal of Medicinal Crop Science
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• v.10 no.3
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• pp.206-211
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• 2002

For developing natural presevatives, essential oils of Mentha arvensis L. var. piperascens Malivaud and Agastache rugosa O. Kuntze were analyzed the composition of two oils and experimented on microorganism survival. Main components of Mentha arvensis oil were isomenthol (26.84%) and menthol (25.48%), and those of Agastache rugosa oil were estragole (79.83%) and limonene (4.13%) from GC-MSD analysis. Inhibition activities of Mentha arvensis oil against growth of Escherichia coli O157 : H7 ATCC 43895 and Salmonella typhimurium ATCC 7988 were observed from their clear zone $(9{\sim}14 mm\;&\;9{\sim}13\;mm)$, and that of Agastache rugosa oil were done from the clear zone $(13{\sim}20 mm\;&\;10{\sim}18\;mm)$ by concentration-dependent manner, respectively. In the inhibition test on CFU/ml of the microorganisms, both of the plant essential oils at concentration of 5 and 10 mg showed potent growth inhibition activities from 9 hour of incubation. Analysis using transmission electron microscope on E. coli also showed antimicrobial activities of the oils as deformation of the cell and loss of the intracellular materials.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.2
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• pp.187-194
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• 2012

The strength of particle-reinforced metal matrix composites is, in general, known to be increased by the geometrically necessary dislocations punched around a particle that form during cooling after consolidation because of coefficient of thermal expansion (CTE) mismatch between the particle and the matrix. An additional strength increase may also be observed, since another type of geometrically necessary dislocation can be formed during extensive deformation as a result of the strain gradient plasticity due to the elastic-plastic mismatch between the particle and the matrix. In this paper, the magnitudes of these two types of dislocations are calculated based on the dislocation plasticity. The dislocations are then converted to the respective strengths and allocated hierarchically to the matrix around the particle in the axisymmetric finite-element unit cell model. The proposed method is shown to be very effective by performing finite-element strength analysis of $SiC_p$/Al2124-T4 composites that included ductile failure in the matrix and particlematrix decohesion. The predicted results for different particle sizes and volume fractions show that the length scale effect of the particle size obviously affects the strength and failure behavior of the particle-reinforced metal matrix composites.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.32 no.6
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• pp.699-705
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• 1999

The effects of iron on gill tissue and metabolic rate represented by oxygen consumption of olive flounder, Paralichthys olivaceus were determined. The effects were further studied by means of survival rate of the fish exposed to a serial concentrations of iron. The olive flounder exposed to iron concentrations over 0.93 mg/$\ell$ showed curvature and terminal clubbing of gill lamellae at 2 weeks post-exposure. In iron concentration 4.89 mg/$\ell$, gill of the fish were seriously damaged just after 2 weeks, showing hyperplasia of filament epithelia, deformation of lamella epithelia, chloride cell damage, and separation of lamella epithelial layer, Gills exposed to 9.78 mg/$\ell$ iron concentration resulted in fusion and necrosis of the lamellae after 2 weeks. Significant decreases of metabolic rate of the fish were observed after 4 weeks at iron concentration 0,93 mg/$\ell$ and after 2 weeks at iron concentrations over 4.89 mg/$\ell$. Survival rate of the olive flounder decreased significantly after 4 weeks at the iron concentration over 4.89 mg/$\ell$. These results lead us to conclude that, as far as the iron effects are concerned, its concentrations should not exceed at least more than 0.93 mg/$\ell$ in the fish farm and coastal waters for normal growth of the olive flounder.

• The Journal of Engineering Geology
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• v.21 no.4
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• pp.349-359
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• 2011

The consolidation behavior of soft clay is controlled mainly by its compressibility and deformation characteristics. Soil permeability depends on various soil characteristics, including the soil type and anisotropy. The coefficient of permeability of soft clay is determined by using a laboratory test (the Oedometer test) or a piezocone test. The latter test is useful for estimating the permeability characteristics from $c_h$ and $k_h$ by performing an excess pore-pressure dissipation test. This study seeks to validate an existing theoretical formula in applying it to marine clay, and to assess the relation between $k_h/k_c$ and the mechanical properties of soft clay. Piezocone tests and laboratory tests were performed using sediment from the Yellow Sea and from the South Sea near Korea. We compared $k_h/k_v$ values obtained using the piezocone test and using laboratory consolidation tests. The obtained values are similar to the values obtained by Jamiolkowski et al. (M application); therefore, the latter values are recommended to be used as $k_h/k_v$.

• Journal of the Korea institute for structural maintenance and inspection
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• v.6 no.3
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• pp.201-209
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• 2002

Crib wall system is one of segmental crib type wall. Crib walls are constructed from separate members with no bonds between them other than frictional. The wall units are divide into two main types termed headers and stretchers. The headers run from the front to the back of the wall, perpendicular to the wall face. The cells are created by forming a grid by stacking individual wall components known as headers and stretchers. The body of wall consists of a system of open cell which are filled with a granular material. The design of crib retaining wall is usually based on conventional design methods derived from Rankine and Coulomb theory so that is able to resist the thrust of soil behind it, because it may be assumed that the wall acts as a rigid body. However, deformation characteristics of crib walls cannot be assumed as monolithic. They consist of individual members which have been stacked to creat a three dimensional grid. Therefore, the segmental grid allows relative movement between the individual member within the wall. The three dimensional flexible grid leads to stress distribution by interaction behavior between soil and crib wall. Therefore, in this study, in order to analysis the trends of deflection of crib wall system, new numerical models based on the results of Brandl's full scale test are introduced for design concept.

• Journal of the Korean GEO-environmental Society
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• v.12 no.12
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• pp.47-54
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• 2011

Consolidation behavior of soft clay is generally to be affected by its compressibility and deformation characteristics. Especially, soil permeability depends on soil characteristics including its type of anisotropy. Coefficient of permeability of soft clay is mostly estimated by using laboratory(Oedometer test) and in-stiu piezocone test. The permeability characteristics of soft clay is estimated by excess pore pressure dissipation test results. In this study, the tests were performed to find out the validity of the existing theoretical formula in clay by pore pressure dissipation test and laboratory test results. After grasping of variation the coefficient of permeability ratio(${k_{h}/k_{v}}$) in different clay soils, it was found out adequate solution of in-stiu permeability ratio(${k_{h}/k_{v}}$). Piezocone tests and laboratory tests were performed at the site of pilot project of ground improvement at Yangsan-Mulgeum, Gyeongsangnam-do. Comparisons of the estimated values of ${k_{h}/k_{v}}$ using piezocone tests results and those from laboratory consolidation tests were carried out. Test results show that values of ${k_{h}/k_{v}}$ by piezocone test result(5.85) is similar of it's laboratory test(5.28).

• Journal of the Korean Institute of Gas
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• v.25 no.2
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• pp.64-71
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• 2021

Research on polymer matrix composites with excellent molding processability and mechanical properties in the automotive field including hydrogen fuel cell electric vehicles is expanding to Computer-Aided Engineering (CAE) to support the design of materials with specific mechanical properties. CAE automation requires the prediction of the mechanical properties and behavior of materials. Unlike single materials, the mechanical properties prediction of polymer matrix composites is difficult to explain with formulas because the mechanical behavior is complicated to be explained only by the relationship between the matrix and the filler. In this study, the stress-strain curve according to the composition of polymer matrix composites, which was difficult to predict due to its sensitivity to large plastic deformation and composition, was predicted based on machine learning of the test data. The developed model finds a complex correlation between matrix and filler types and compositions, and predicts the total stress-strain curve meaningfully even in the absence of learned test data. It is expected that the material design AI system can be completed in the future based on the developed model that predicts the mechanical properties of polymer matrix composites even for the combination and composition that have not been learned.

• Korean Journal of Poultry Science
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• v.44 no.1
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• pp.19-28
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• 2017

The eggshell is an intricate and highly ordered structure composed of multiple layers and a calcified matrix. The eggshell is formed at the uterine segment of the chicken oviduct. In this study, histological changes in the uterine endometrium and the expression of the eggshell-related genes were investigated according to hen age. We analyzed the expression of eggshell protein-related genes, such as OCX-32, OCX-36, OC-17, OC-116, and eggshell-ion-related genes, such as CABL-1, SPP1, SCNN1G, ATP2A2, CA2, and CALM1. In chicken uterine endometrium, histological deformation, fibrosis, atrophy and elimination of micro-villi were found with increasing hen age. The concentration of blood-ion components did not significantly change with age. The amount of telomeric DNA in uterine endometrial cells decreased with increasing hen age. The expression of most of the eggshell-related genes changed significantly with increasing hen age. The expression of some ovo-proteins, which play a role in eggshell formation, increased with increasing hen age; however, there were no significant correlations among eggshell protein genes. Eggshell ion-related genes, such as ATP2A2, SCNN1G, CA2, and CALM1, were closely related to each other. The OCX-32 and OCX-36 genes were closely related to some of the eggshell ion genes. Eggshell protein-related genes, such as the OCX-32, OCX-36 genes and ion-related genes such as CALB-1, ATP2A2, SCNN1G, CA2, CALM1, affected eggshell formation, mutually or independently. This study shows that, uterine although endometrial cell damage occurs with increasing hen age, normal eggshells can be formed in old hens. This suggests that eggshell protein-and eggshell ion-related genes also control the homeostasis of eggshell formation.